Hi all - I’m having a problem with my microSD Shield. I have the shield up and running and am using it to log data measured by the ADC from an analog sensor to a uSD card. While the recording of data works flawlessly, I noted a lot more noise in my measurements than I expect and more than I see when I have my sensor circuit isolated from my arduino project. I’ve verified with an o-scope that 3.3v power pin on the arduino has a significant amount of obviously digital noise on it. If I unmate the shield the noise goes away on the 3.3v pin, and if I comment out the SPI writes to the SD card, the noise likewise vanishes. There is no noticeable noise on the 5.0v pin. I have decoupling capacitors at the sensors and on the power buses. Is this a design flaw of the shield, a defective part, or could I have a ground loop (and how do I check for one) ? I’d appreciate any help anyone can offer! Thanks!
Scott